The International Agency for Research on Cancer (IARC), which is part of the World Health Organisation (WHO), has classified diesel engine exhaust as carcinogenic to humans, based on sufficient evidence that exposure is associated with an increased risk of lung cancer.
In a statement, the IARC said the classification was made after a week-long meeting of international experts in Lyon, France.
In 1988, IARC classified diesel exhaust as probably carcinogenic to humans.
There has been mounting concern about the cancer-causing potential of diesel exhaust, particularly based on findings in epidemiological studies of workers exposed in various settings.
This was re-emphasized by the publication in March 2012 of the results of a large US National Cancer Institute/National Institute for Occupational Safety and Health study of occupational exposure to such emissions in underground miners, which showed an increased risk of death from lung cancer in exposed workers.
The scientific evidence was reviewed thoroughly by the Working Group and overall it was concluded that there was sufficient evidence in humans for the carcinogenicity of diesel exhaust.
The Working Group found that diesel exhaust is a cause of lung cancer (sufficient evidence) and also noted a positive association (limited evidence) with an increased risk of bladder cancer.
The Working Group concluded that gasoline exhaust was possibly carcinogenic to humans (Group 2B), a finding unchanged from the previous evaluation in 1989.
Large populations are exposed to diesel exhaust in everyday life, whether through their occupation or through the ambient air.
People are exposed not only to motor vehicle exhausts but also to exhausts from other diesel engines, including from other modes of transport (e.g. diesel trains and ships) and from power generators.
Increasing environmental concerns over the past two decades have resulted in regulatory action in North America, Europe and elsewhere with successively tighter emission standards for both diesel and gasoline engines.
The statement quoted Christopher Portier, Chairman of the IARC working Group, as saying that the scientific evidence ”was compelling and the Working Group’s conclusion was unanimous: diesel engine exhaust causes lung cancer in humans”.
He said given the additional health impacts from diesel particulates, exposure to this mixture of chemicals should be reduced worldwide.
For his part, Christopher Wild, Director, IARC, said while IARC’s remit is to establish the evidence-base for regulatory decisions at national and international level, the conclusion sends a strong signal that public health action is warranted.